To achieve lighter weight and smaller size in automobile engines, a cylinder block made of aluminum alloy is often fitted with cylinder liners made of cast iron. As the method for producing such a cylinder block fit with cylinder liners, the method is known of setting cylinder liners in advance in a casting mold for the cylinder block, pouring the casting material (aluminum alloy) into this casting mold, and thereby covering the outer circumferences of the cylinder liners with aluminum alloy.
In recent years, to increase engine output and lower fuel consumption, the areas near top dead center in the cylinder bores have become thermally harsher in conditions. Further, to achieve lower fuel consumption, there has been a demand to reduce the wall thicknesses between the cylinder bores so as to lighten the weight of the engine. To meet with such demands, in the past, the cylinder liners for insert casting use shown in Japanese Patent Publication (A) No. 2007-16733 have been known. These cylinder liners for insert casting use are improved in bond strength and thermal conductivity with the cylinder block. They are provided with thin undercut projections on their outer circumferential surfaces on which, in turn, thermally sprayed layers are formed. As the material of the thermally sprayed layers, an Al—Si alloy or other aluminum alloy or copper or a copper alloy is used.